Scientists: Parasite makes mice unafraid of cats (video)

A common parasite that can make cats dangerous for pregnant women also makes mice unafraid of cats, scientists have found.

The parasite toxoplasma gondhii, which commonly lives in the digestive tract of cats, alters the brain function in mice that naturally makes them flee at the sight or smell of a feline, Smithsonian magazine reports on its website.

“It rewires a mouse’s brain to suppress the fear of cats,” Smithsonian’s Kelly Carnes says in a video posted this week.

The parasite is common in cats and, according to the Centers for Disease Control and Prevention, infects about 60 million humans in the U.S., though most are unaware of the infection and show no symptoms. The bug is responsible for the disease toxoplasmosis, to which pregnant women are especially vulnerable, and has been linked to behavioral changes and schizophrenia in humans.

The parasite's effect on cats was first reported in the journals PLOS ONE and Nature in September.

The effect on infected mice continues for several months even after the parasites are removed, scientists found.